关于JAVA的线程问题

import java.util.Date;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
public class MyThreadTest {
	
	public static void main(String[] args){
		boolean flag = true;
		Set<Long>threadSet = new HashSet<Long>();
		long last = -1;
		long now = 0;
		
		Runtime runtime = Runtime.getRuntime(); 
		while(true){
			
			MyThread thread = new MyThread(flag);
			thread.start();
			
			threadSet.add(thread.getId());
			if(last == now){
				System.out.println("PAY ATTATION ! THE MOST THREADS IS " + threadSet.size());
				flag = false;
			}else{
				last = now;
				now = threadSet.size();
			}
			
			if(System.currentTimeMillis() % 3000 == 0){
				System.out.println("NOW THE THREADS NUMBER IS " + threadSet.size());
				System.out.println("NOW ACTIVITY THREAD NUMBER IS " + Thread.getAllStackTraces().size());
				if(System.currentTimeMillis() % 10000 == 0){
					 System.out.println("FREE MEMORY IS ---------------------- > " + runtime.freeMemory() / 1024);
					 System.out.println("TOTAL MEMORY IS --------------- > " + runtime.totalMemory() / 1024);
					 System.out.println("MAX MEMORY IS ----------------- > " + runtime.maxMemory() / 1024);
				}
			}
		}
	}
	
}
class MyThread extends Thread{
	public MyThread(final boolean flag) {
		Runnable runnable = new Runnable() {
			public void run() {
				while (flag) {
					new Date();
				}
			}
		};
	}
}

NOW THE THREADS NUMBER IS 1689019
NOW ACTIVITY THREAD NUMBER IS 6
FREE MEMORY IS ---------------------- > 19279
TOTAL MEMORY IS --------------- > 145920
MAX MEMORY IS ----------------- > 908288
NOW THE THREADS NUMBER IS 2239629
NOW ACTIVITY THREAD NUMBER IS 6
FREE MEMORY IS ---------------------- > 112022
TOTAL MEMORY IS --------------- > 268800
MAX MEMORY IS ----------------- > 908288
NOW THE THREADS NUMBER IS 2835575
NOW ACTIVITY THREAD NUMBER IS 6
FREE MEMORY IS ---------------------- > 90645
TOTAL MEMORY IS --------------- > 275968
MAX MEMORY IS ----------------- > 908288

NOW ACTIVITY THREAD NUMBER IS 6
FREE MEMORY IS ---------------------- > 79341
TOTAL MEMORY IS --------------- > 284672
MAX MEMORY IS ----------------- > 908288
NOW THE THREADS NUMBER IS 3131343

java.lang.OutOfMemoryError: GC overhead limit exceeded